I solved this. I made a small DLL in Delphi to do this:
1. enumerating all processes and scan for the required executable.
2. Then enumerating all windows, which belong to this process. And get the one with no parent-handle.
Finally, back in Windev, I had to CallDLL32("User32.dll","SetForegroundWindow",nHandle)
I will post a small demo-project under solutions, these days.
Arie